ASTM D6034-96(2004)

Standard Test Method (Analytical Procedure) for Determining the Efficiency of a Production Well in a Confined Aquifer from a Constant Rate Pumping Test

SCOPE
1.1 This test method describes an analytical procedure for determining the hydraulic efficiency of a production well in a confined aquifer. It involves comparing the actual drawdown in the well to the theoretical minimum drawdown achievable and is based upon data and aquifer coefficients obtained from a constant rate pumping test.  
1.2 This analytical procedure is used in conjunction with the field procedure, Test Method D 4050.
1.3 Limitations- The limitations of the technique for determination of well efficiency are related primarily to the correspondence between the field situation and the simplifying assumption of this test method.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2004
• ICS: 93.160 - Hydraulic construction
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.21 - Groundwater and Vadose Zone Investigations

Relations

• Replaces: ASTM D6034-96 - Standard Test Method (Analytical Procedure) for Determining the Efficiency of a Production Well in a Confined Aquifer from a Constant Rate Pumping Test
• Effective Date: 01-Nov-2004
• Replaced By: ASTM D6034-96(2010)e1 - Standard Test Method (Analytical Procedure) for Determining the Efficiency of a Production Well in a Confined Aquifer from a Constant Rate Pumping Test
• Effective Date: 01-Aug-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6034 – 96 (Reapproved 2004)
Standard Test Method (Analytical Procedure) for
Determining the Efficiency of a Production Well in a
Confined Aquifer from a Constant Rate Pumping Test
This standard is issued under the fixed designation D6034; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 aquifer, confined, n—an aquifer bounded above and
1.1 This test method describes an analytical procedure for
below by confining beds and in which the static head is above
determining the hydraulic efficiency of a production well in a
the top of the aquifer.
confinedaquifer.Itinvolvescomparingtheactualdrawdownin
3.2.2 confining bed, n—a hydrogeologic unit of less perme-
the well to the theoretical minimum drawdown achievable and
able material bounding one or more aquifers.
is based upon data and aquifer coefficients obtained from a
3.2.3 control well, n—a well by which the head and flow in
constant rate pumping test.
the aquifer is changed, for example, by pumping, injection, or
1.2 Thisanalyticalprocedureisusedinconjunctionwiththe
imposing a constant change of head.
field procedure, Test Method D4050.
3.2.4 drawdown, n—vertical distance the static head is
1.3 Limitations—The limitations of the technique for deter-
lowered due to the removal of water.
mination of well efficiency are related primarily to the corre-
3.2.5 hydraulic conductivity, n—(field aquifer test) the vol-
spondence between the field situation and the simplifying
umeofwaterattheexistingkinematicviscositythatwillmove
assumption of this test method.
in a unit time under a unit hydraulic gradient through a unit
1.4 This standard does not purport to address all of the
area measured at right angles to the direction flow.
safety concerns, if any, associated with its use. It is the
3.2.6 observation well, n—a well open to all or part of an
responsibility of the user of this standard to establish appro-
aquifer.
priate safety and health practices and determine the applica-
3.2.7 piezometer, n—a device so constructed and sealed as
bility of regulatory limitations prior to use.
to measure hydraulic head at a point in the subsurface.
2. Referenced Documents 3.2.8 storage coeffıcient, n—the volume of water an aquifer
releases from or takes into storage per unit surface area of the
2.1 ASTM Standards:
aquifer per unit change in head.
D653 Terminology Relating to Soil, Rock, and Contained
3.2.9 transmissivity, n—the volume of water at the existing
Fluids
kinematic viscosity that will move in a unit time under a unit
D4050 Test Method for (Field Procedure) for Withdrawal
hydraulic gradient through a unit width of the aquifer.
and Injection Well Tests for Determining Hydraulic Prop-
3.2.10 well effıciency, n—the ratio, usually expressed as a
erties of Aquifer Systems
percentage, of the measured drawdown inside the control well
D5521 Guide for Development of Ground-Water Monitor-
divided into the theoretical drawdown which would occur in
ing Wells in Granular Aquifers
the aquifer just outside the borehole if there were no drilling
3. Terminology
damage, that is, no reduction in the natural permeability of the
sediments in the vicinity of the borehole.
3.1 Definitions—For definitions of terms used in this test
3.3 Symbols:Symbols and Dimensions:
method, see Terminology D653.
−1
3.3.1 K—hydraulic conductivity [LT ].
3.3.1.1 Discussion—The use of the symbol K for the term
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
hydraulic conductivity is the predominant usage in ground-
RockandisthedirectresponsibilityofSubcommitteeD18.21onGroundWaterand
water literature by hydrogeologists, whereas the symbol k is
Vadose Zone Investigation.
commonly used for this term in soil and rock mechanics and
Current edition approved Nov. 1, 2004. Published December 2004. Originally
approved in 1996. Last previous edition approved in 1996 as D6034–96. DOI:
soil science.
10.1520/D6034-96R04.
3.3.2 K—hydraulicconductivityintheplaneoftheaquifer,
2 r
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
radially from the control well (horizontal hydraulic conductiv-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
−1
Standards volume information, refer to the standard’s Document Summary page on
ity) [LT ].
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6034 – 96 (2004)
3.3.3 K —hydraulic conductivity normal to the plane of the
z
−1
aquifer (vertical hydraulic conductivity) [ LT ].
3.3.4 K (x)—modified Bessel function of the second kind
and zero order [nd].
3 −1
3.3.5 Q—discharge [L T ].
3.3.6 S—storage coefficient [nd].
2 −1
3.3.7 T—transmissivity [L T ].
3.3.8 s—drawdown in the aquifer at a distance r from the
r
control well [ L].
3.3.9 s—drawdown which would occur in response to
f
pumping a fully penetrating well [L].
3.3.10 r —borehole radius of control well [L].
w
3.3.11 s —theoreticaldrawdownwhichwouldoccurinthe
rw
aquifer just outside the borehole if there were no drilling
damage, that is, no reduction in the natural permeability of the
FIG. 1 Illustration of Drawdown Inside and Outside Pumping Well
sediments in the vicinity of the borehole [L].
3.3.12 s —drawdown measured inside the control well [L].
w
3.3.13 u—(r S)/(4Tt)[nd]. intake. While these drawdown components contribute to inef-
ficiency, they usually are minor in comparison to the head loss
3.3.14 W(u)—an exponential integral known in hydrology
as the Theis well function of u [nd]. resulting from drilling damage.
4.2.2 Thewellefficiency,usuallyexpressedasapercentage,
3.3.15 A—K /K , anisotropy ratio [nd].
z r
3.3.16 b—thickness of aquifer [ L]. is defined as the theoretical drawdown, also called aquifer
drawdown, which would have occurred just outside the well if
3.3.17 d—distance from top of aquifer to top of screened
interval of control well [L]. there were no drilling damage divided by the actual drawdown
inside the well. The head losses contributing to inefficiency
3.3.18 d8—distance from top of aquifer to top of screened
interval of observation well [L]. generally are constant with time while aquifer drawdown
gradually increases with time. This causes the computed
3.3.19 f —incremental dimensionless drawdown compo-
s
nent resulting from partial penetration [nd]. efficiencytoincreaseslightlywithtime.Becausetheefficiency
issomewhattimedependent,usuallyitisassumedthatthewell
3.3.20 l—distancefromtopofaquifertobottomofscreened
efficiency is the calculated drawdown ratio achieved after one
interval of control well [L].
day of continuous pumping. It is acceptable, however, to use
3.3.21 l8—distance from top of aquifer to bottom of
other pumping times, as long as the time that was used in the
screened interval of observation well [L].
efficiency calculation is specified. The only restriction on the
3.3.22 r—radial distance from control well [L].
pumping time is that sufficient time must have passed so that
3.3.23 t—time since pumping began [ T].
3.3.24 E—well efficiency [nd]. wellbore storage effects are insignificant. In the vast majority
of cases, after one day of pumping, the effects of wellbore
4. Summary of Test Method
storage have long since become negligible.
4.1 Thistestmethodusesdatafromaconstantratepumping
4.2.3 Efficiency is also somewhat discharge dependent.
test to determine the well efficiency. The efficiency is calcu-
Boththeaquiferdrawdownandtheinefficiencydrawdowncan
latedastheratioofthetheoreticaldrawdownintheaquiferjust
include both laminar (first order) and turbulent (approximately
outsidethewellbore(s )tothedrawdownmeasuredinsidethe
second order) components. Because the proportion of laminar
r
w
pumped well (s ). The theoretical drawdown in the aquifer
versusturbulentflowcanbedifferentintheundisturbedaquifer
w
(s ) is determined from the pumping test data by either
than it is in the damaged zone and inside the well, the aquifer
r
w
extrapolation or direct calculation.
drawdown and inefficiency drawdown can increase at different
4.2 During the drilling of a well, the hydraulic conductivity
rates as Q increases. When this happens, the calculated
of the sediments in the vicinity of the borehole wall is reduced
efficiency is different for different pumping rates. Because of
significantly by the drilling operation. Damaging effects of
this discharge dependence, efficiency testing usually is per-
drilling include mixing of fine and coarse formation grains,
formed at or near the design discharge rate.
invasion of drilling mud, smearing of the borehole wall by the
4.3 Thedrawdownintheaquiferaroundawellpumpedata
drillingtools,andcompactionofsandgrainsneartheborehole.
constant rate can be described by one of several equations.
The added head loss (drawdown) associated with the perme-
4.3.1 For fully penetrating wells, the Theis equation (1) is
ability reduction due to drilling damage increases the draw-
used.
downinthepumpedwellandreducesitsefficiency(seeFig.1).
Q
s 5 W~u! (1)
Well development procedures help repair the damage (see
r
4pT
Guide D5521) but generally cannot restore the sediments to
where:
their original, natural permeability.
4.2.1 Additional drawdown occurs from head loss associ-
ated with flow through the filter pack, through the well screen
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
and vertically upward inside the well casing to the pump this test method.
D6034 – 96 (2004)
2x
e
s = numerator, must be determined from field data.
`
rw
W~u! 5 dx (2)
*u
x
Two procedures are available for determining s —
rw
extrapolation and direct calculation.
and
4.4.1 Extrapolation—Extrapolation can be used to deter-
r S
mine s if data from two or more observation wells are
u 5 (3)
r
w
4Tt
available. Distance drawdown data can be plotted from these
4.3.2 For sufficiently small values of u, the Theis equation
wells on either log-log or semilog graphs. If a log-log plot is
may be approximated by the Cooper-Jacob equation (2).
used,theTheistypecurveisusedtoextrapolatethedrawdown
data to the borehole radius to determine s . If a semilog plot
2.3Q 2.25Tt
r
w
s 5 log (4)
r S 2 D
is used, extrapolation is done using a straight line of best fit.
4pT
r S
The semilog method can be used only if the u value for each
4.3.2.1 Examplesoferrorsinthisapproximationforsome u
observation well is sufficiently small that the error introduced
values are as follows:
by the log approximation to the Theis equation is minimal.
u Error
4.4.1.1 Forpartiallypenetratingwells,theobservationwells
0.01 0.25 %
must be located beyond the zone affected by partial penetra-
0.03 1.01 %
0.05 2.00 %
tion, that is, at a distance r from the pumped well such that:
0.10 5.35 %
1.5b
r$ (9)
4.3.3 For partially penetrating wells, the drawdown can be
K /K
=
z r
described by either the Hantush equation (3-5) or the Kozeny
4.4.1.2 The extrapolated drawdown obtained in this case is
equation (6).
s, the theoretical drawdown, which would have occurred just
f
4.3.3.1 The Hantush equation is similar to the Theis equa-
outside the borehole of a fully penetrating pumped well. The
tion but includes a correction factor for partial penetration.
aquifer drawdown corresponding to partial penetration is then
Q
computed with the Hantush equation as follows:
s 5 ~W~u! 1 f ! (5)
r s
4pT
Q
s 5 s 1 f (10)
4.3.3.2 According to Hantush, at late pumping times, when
r f s
w
4pT
t > b S/(2TA), f can be expressed as follows:
s
4.4.1.3 The second term on the right-hand side of Eq 10
`
4b 1 npr =K /K
z r represents the incremental aquifer drawdown caused by partial
f 5 K (6)
s ( 0
2 S 2D S D
b
p ~l– d!~l8– d8! n 51 n
penetration.
4.4.1.4 Using the Kozeny equation, the aquifer drawdown
npl npd npl npd
sin –sin sin – sin
F S D S DGF S D S DG
for partial penetration is computed from Eq 7 with r set equal
b b b b
to the borehole radius r :
w
4.3.3.3 The Kozeny equation is as follows:
s
f
s
f s 5 (11)
r
w
s 5 (7)
l 2 d r p~l 2 d!
r
w
l 2 d r p~l 2 d!
1 17 cos
S D
Œ
b 2b
1 17 cos 2~l 2 d!
S ΠD
b 2b
2~l– d!
4.4.1.5 If the extrapolation method is used for determining
4.3.3.4 In this equation, sis the drawdown for a fully
f
aquifer drawdown, it is not necessary to make a separate
penetrating well system and can be computed from Eq 1-4.
adjustment to account for boundaries or recharge.
While easier to compute than the Hantush equation, the
4.4.2 Direct Calculation—If the aquifer drawdown s can-
rw
Kozeny equation is not as accurate. It does not incorporate
not be obtained by extrapolation, direct calculation must be
pumping time or anisotropy and assumes that the screen in the
used to determine its value.
control well reaches either the top or the bottom of the aquifer.
4.4.2.1 For fully penetrating wells, s can be obtained by
rw
4.3.4 The presence of a positive boundary (for example,
direct calculation using either the Theis or Cooper-Jacob
recharge) causes the drawdown in the aquifer to be less than
equations (Eq 1-4).
predicted by Eq 1-6, while a negative boundary (for example,
4.4.2.2 For partially penetrating wells, s is calculated from
r
w
the aquifer pinching out) results in more drawdown. The
the Hantush equation (Eq 5 and Eq 6) or the Kozeny equation
boundary-induced increases or decreases in drawdown usually
(Eq 11).
canbedeterminedfromthepumpingtestdata.Theseincreases/
4.4.2.3 The presence of aquifer boundaries or recharge will
decreases can be combined with calculations using Eq 1-7 to
tendtoincreaseordecrease,respectively,thedrawdowninand
determine the drawdown just outside the well bore.
aroundthepumpedwell.Whentheyarepresent,thecalculated
4.4 The efficiency of a production well is calculated as
value of s must be adjusted to reflect the impact of the
r
w
follows:
boundary conditions.
s
r
w
E 5 (8)
5. Significance and Use
s
w
5.1 This test method allows the user to compute the true
where:
hydraulic efficiency of a pumped well in a confined aquifer
s = denominator, the drawdown measured inside the
w
from a constant rate pumping test. The procedures described
well, and
constitutetheonlyvalidmethodofdeterminingwellefficiency.
D6034 – 96 (2004)
Somepractitionershaveconfusedwellefficiencywithpercent- Finally, check the background water-level fluctuations ob-
age of head loss associated with laminar flow, a parameter served prior to or following the pumping test to see if
commonly determi
...